WASHINGTON: The United States said on Thursday (Oct 11) that it will increasingly restrict civilian nuclear exports to China as President Donald Trump vowed a hard line on trade, bluntly warning not to think Americans are "stupid."

"The United States cannot ignore the national security implications of China's efforts to obtain nuclear technology outside of established processes of US-China civil nuclear cooperation," Energy Secretary Rick Perry said in a statement.

The US already carefully reviews nuclear exports through the Energy Department's so-called Part 810 authorisations, which verify if the technology goes to peaceful use and will not be sent to a third country.

The United States last year shipped US$170 million in nuclear exports to China, according to official figures.

Former president Barack Obama in 2015 signed off on an extension of nuclear cooperation between the United States and China, with his administration arguing that Beijing had moved to tighten controls as part of renewal negotiations.